Electrical stimulations of dorsal cutaneous nerves (DCNs) at each lumbothoracic spinal level produce the bilateral cutaneus trunci muscle (CTM) reflex responses which consist of two temporal components: an early and late responses purportedly mediated by Aδ and C fibers, respectively. We have previously reported central projections of DCN A and C fibers and demonstrated that different projection patterns of those afferent types contributed to the somatotopic organization of CTM reflex responses. Unilateral hemisection spinal cord injury (SCI) was made at T10 spinal segments to investigate the plasticity of early and late CTM responses 6 weeks after injury. Both early and late responses were drastically increased in response to both ipsi- and contralateral DCN stimulations both above (T6 and T8) and below (T12 and L1) the levels of injury demonstrating that nociceptive hyperreflexia developed at 6 weeks following hemisection SCI. We also found that DCN A and C fibers centrally sprouted, expanded their projection areas, and increased synaptic terminations in both T7 and T13, which correlated with the size of hemisection injury. These data demonstrate that central sprouting of cutaneous afferents away from the site of injury is closely associated with enhanced responses of intraspinal signal processing potentially contributing to nociceptive hyperreflexia following SCI.

中文翻译：

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大鼠脊髓损伤后皮肤传入神经的中心可塑性与伤害性反射亢进相关。

在每个lumbothoracic脊髓水平背侧皮神经（的DCN）的电刺激产生双边cutaneus trunci肌肉（CTM），其由两个时间分量的反射反应：一个早期和晚期应答由A据称介导δ和C纤维。我们之前已经报道了DCN A和C纤维的中心投影，并证明了这些传入类型的不同投影模式有助于CTM反射反应的体位组织。在T10脊髓节段进行单侧半截断脊髓损伤（SCI），以研究损伤后6周早期和晚期CTM反应的可塑性。高于（T6和T8）和低于（T12和L1）损伤水平时，对同侧和对侧DCN刺激的反应，早期和晚期反应均显着增加，表明伤害性反射亢进发生在半切SCI后6周。我们还发现DCN A和C纤维集中发芽，扩大了其投射区域，并增加了T7和T13的突触末端，与半切伤的大小有关。这些数据表明，远离损伤部位的皮肤传入芽的中央发芽与脊髓内信号处理的增强反应密切相关，可能会导致SCI后的伤害性反射亢进。